I want huge chainrings on my MTB, any suggestions appreciated!
 

BIANCHI LYNX 1997

Component Group Shimano Alivio/AceraX
Brakeset Shimano Altus brakes, Shimano Alivio levers
Shift Levers Grip Shift SRT-400i
Front Derailleur Shimano AceraX top-swing, bottom-pull/clamp-on 28.6 mm
Rear Derailleur Shimano Alivio
Crankset Shimano Alivio, 22/32/42 teeth
Bottom Bracket Shimano BB-LP26, 113 mm spindle
BB Shell Width 68mm English
Rear Cogs 7-speed, 11 - 28 teeth
Chain KMC HG-50, 1/2 x 3/32"
Tires 26 x 1.95" Kenda K-850

I don't have much time to bike (~25 min every other day), so for cardio I jump on my bike and mash up and down the biggest hills I can find. I want to be able to pass cars on the way down. I've considered getting slicks for speed, but with the 42t I currently have, my cadence would have to be about 250+ in order to push the bike much, which would obviously look ridiculous.

I know I have a mediocre bike, and the LBS tells me to buy new, but even if I did buy new I'd still have to do all the upgrades that upgrading this Bianchi would require (because the stock cranksets on entry-level new road bikes are severely under-powered for my riding style). I'd like a 53t or even up to a 60t for my largest chainring up front.

My front derailleur needs replacing anyway, and I rarely go on trails so I'm not worried about getting over logs. Is it possible to do something like 30/42/55t? What other than the front derailleur would need to be replaced?

Thanks a lot, Mashy McGee

A road triple would give you 50-39-30. Depending on the crankset you swap in, you may need to change your bottom bracket as well.

Mashing big gears is not helpful to get your cardio. Your heart pumps harder when you spin high RPMs.

I have not seen too many chainrings larger than 53 tooth for a decade or more. They are out there but are a specialty item.

AFAIK, your crank has the chainrings riveted on so you can't change them. That leaves you needing a new crank and bottom bracket and almost certainly a new front derailleur. Your chain is likely too short for the larger chainring so add the cost of a new one. Finally, your front shifter is made to work with an MTB front derailleur and won't work properly with a road front derailleur so plan on changing it too. This is getting expensive isn't it?

Quite possibly a decent quality used road bike from Craigs List would be simpler and cheaper.

Outer chainring can easily be replaced with a 48T. You'll need to raise the front derailleur.

Shimano sells the same cranks with "MTB" chainrings of about 44/32/22 or "touring/trekking/hybrid" chainrings of about 48/36/26.

road triple crank with shimano flat bar road FD r443 would get you what you desire. Do that and throw some road slicks on there while your at. check out nashbar for an inexpensive road crank and bottom bracket and hvae a blast. you can do this upgrade for about $120 if your capable of doing the labor yourself. if you have to pay an lbs probably looking at 15 or 20 bucks for them to swap the cranks for you

A Schlumpf Speed drive , an IG crankset , multiplies what gear you have
by 1.6 , so like a 38T ring is still physically 38t in size, but in overdrive
acts like its 60.8t, that should be big enough for anyone..

combine that with a 9x3 dual Drive hub in the back wheel..
and you can fly or climb at will.

You should also note that just because you have bigger chainrings doesn't mean you'll suddenly be able to spin them fast enough to pass cars. Wind resistance will always be the limiting factor for a cyclist's speed given our universally low power outputs. Keep in mind that pro sprinters get by with a 53 tooth chainring. I can assure you that you don't need more gearing than they do.

Are you sure the big chainring on the Alevio crank is replacable? The pictures I Googled up make it look like the outer ring is one piece with the spider.

+1
If you want to pass cars get a road bike. Road components don't work well on mountain bikes and ultimately you're talking about more money than you would spend on a decent road bike. Also you'd have a lot of frustration trying to make the components compatible.

Pretty sure. http://www.dirtbikebitz.com/shimano-...k-p-14910.html

Fietsbob, that speed drive is just insane, but hey why settle for a measly 1.65 when you can get the high speed 2.5x unit.

http://www.schlumpf.ch/hp/hsd/hsd_engl.htm

Mashy, FYI the highest I found (for road bikes though) is 56T at ribble. Stronglite has up to 46T for MTB downhill, but it sounds like you need the Schlumf gear!

http://www.ribblecycles.co.uk/sp/roa...ng/STROCHRI450

http://www.stronglight.com/stronglig...keyProd=94mmdh

I'm not sure. I had a '95 Alivio and the chainrings definitely were NOT replacable as they were welded together. Maybe the newer Alivio's are swappable, but I'm really not sure about back then.

Really huge?? My Rans Tailwind had 20 inch tires, so the chain rings were larger. The largest one was a 62. If that is what you want Rans or a recumbent dealer should be able to get it for you.

Bike Friday used the same 62T ring on it's 20" wheel travel bikes before they had the Shimano Caprio 9x26 cassette available. It looks like a dinner plate and seems to approach the size of the wheel itself. :)

Wasn't thinking about old ones. Probably is riveted: http://sheldonbrown.com/bbsize.html#acera

If it were me, I'd get a trekking crank with 48/38/28T (or something similar for the inner and middle), get a new bottom bracket (if necessary), get a new chain (if necessary), raise the front derailleur, and get a new cable (if necessary).

Actually, I'd look for a used bike that better fit my needs.

Also, OP, I think you're a little overly optimistic to think a 53/11 gear of a road bike won't be high enough for you. With 700c wheels at 120 RPM, that's over 45 MPH. Of course if you're mashing along at 60 RPM, that's closer to 23 MPH. Learn to spin and you can effectively increase your gearing as well as the quality of your cardio workout.

There's no reason you'd need to acquire a new bike in order to be able to pass cars. An old, rigid mountain bike, with the proper tires and gearing, can be extremely fast and stable and will have no trouble doing this. But as others have said, it's going to take some work. However, if you're handy, it's NOT going to take too much money. If you're not handy or would rather get this done as quickly as possible, start stalking cheap used road bikes on Craigs List. Note that the 700c road wheel size is going to give you the gearing you want with smaller chainrings than you'd need for the same gearing on the 26" mountain wheel size.

Before you do any of this, though, make sure you replace those tires with the skinniest, highest-pressure slicks you can fit -- something like these. Your current Kenda K-850 knobbies are slowing you down big time. Replacing them is going to make the biggest difference.

It's easy to tell if your crankset is riveted or bolted -- Just look for the bolts. Alivios can be either, depending on the vintage. If there's no option to unscrew them, it's riveted. Don't despair, though. With some riveted cranksets, you can saw/drill/Dremel the rivets off and replace the chainrings with standard ones and standard chainring bolts. Check the bolt circle diameter of your crank and see if it's one of the standard diameters, then acquire appropriate chainrings to match. Note that since this is an older mountain crank, it's probably got the older 5-spindle 110mm BCD, and even if it's a newer one with the 4-spindle 104mm BCD, it will be hard to find really big chainrings to fit, if you want to avoid buying a "road crank". If you do decide to buy a road crank, just buy any square-taper road triple you can find on eBay, and note that the 52T outer chainring on a standard road crank is a LOT bigger than the 42T you're currently running. As long as you get a square-taper crank, you probably do *not* have to replace the bottom bracket, as long as your FD will swing through the entire range of the new triple.

Note that in order to actually shift a significantly bigger outer chainring, you're going to not only need to raise the derailleur, but in the first place, you need to have a derailleur whose shape gets closer to matching the arc of the bigger chainring. To make a smaller derailleur do this, you can grind away some metal to make the shape match. I've successfully done this myself. See Sheldon. Based on the fact that your bike came with a 42T outer ring, I'm going to guess you've got the "smallest" Alivio FD, which is probably shaped for 44 or 48T max. If you are going to buy a new FD, because your shifters are Grip Shift SRT-400i, I believe the left "front" one is *not* indexed (only "micro-indexed") -- so it will work with *any* derailleur, including any "road" derailleur. Grab a cheap road derailleur on eBay or from the discarded parts bin at your local bike shop. If it is truly "indexed" (only three clicks through its entire range) I'll second motobecane69's recommendation and say get the FD-R443, which is the only "big chainring" FD that Shimano makes that has the "mountain" cable pull as opposed to "road" cable pull -- the difference matters for indexed shifters but not for non-indexed ones.

Good luck!

People do realize this is a joke account, right?

+1

I recently got a cross bike to go alongside my MTB. Going from the MTB riding position to a more aero position, fat tyres to think tyres, and a 44/32/22 to 50/39/30 chainrings coupled with 26" to 29" wheels has seen my speeds increase. The most significant increase I've noticed is climbing where my speeds are anything up to 50% higher on the cross bike than the MTB. I've only tried a few fast downhills (and on two of those I got stuck behind a car) but I've seen my biggest issue as the speed goes up is wind resistance.

Also add another vote to say you probably don't need higher gearing than Mark Cavendish.

You clearly need a 77T chainring for your purposes

http://bikeforums.net/attachment.php...hmentid=213121

While the screen name is a bit of a joke, the post seems sincere enough. He's not the first person to think all they need is bigger chainrings to go faster either.